linux-kernel - Re: [PATCH 0/4] perf annotate: Use libcapstone as a disasssembler

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Date: Fri, 29 Mar 2024 09:32:45 -0700
From: Ian Rogers <irogers@...gle.com>
To: Namhyung Kim <namhyung@...nel.org>, Changbin Du <changbin.du@...wei.com>
Cc: Arnaldo Carvalho de Melo <acme@...nel.org>, Kan Liang <kan.liang@...ux.intel.com>, 
	Jiri Olsa <jolsa@...nel.org>, Adrian Hunter <adrian.hunter@...el.com>, 
	Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...nel.org>, 
	LKML <linux-kernel@...r.kernel.org>, linux-perf-users@...r.kernel.org
Subject: Re: [PATCH 0/4] perf annotate: Use libcapstone as a disasssembler

On Thu, Mar 28, 2024 at 4:20 PM Namhyung Kim <namhyung@...nel.org> wrote:
>
> Hello,
>
> As we've added libcapstone support, it's natural to use it for perf annotate
> as well.  This change added the capstone support on x86 first.  Other archs
> can be added later (by someone who can verify it doesn't break things).
>
> For now it tries to use capstone (if available) before objdump.  But it
> doesn't support source file and line number info.  So users should use the
> objdump (by passing --objdump=PATH option) if they need them.  For example,
> this command line will keep the existing behavior (i.e. using objdump).
>
>   # not to use capstone for disassembly
>   $ perf annotate --objdump=objdump
>
> The capstone uses LLVM objdump style output which is slightly different than
> the GNU objdump.  But it should not have differences besides that.  I've
> verified the result of data type profiling and it produced the same output
> but gave me ~3x speedups.
>
> Thanks,
> Namhyung

I wanted to see what -fsanitize=address would think of libcaptstone
and no issues,  so:

Tested-by: Ian Rogers <irogers@...gle.com>

Some thoughts:
 - it may be worth adding to the commit message in "perf annotate:
Split out util/disasm.c" that there's no functional change,
 - we lack perf annotate testing,
 - it seems capstone should be opt-out rather than opt-in as a library
dependency (given the performance delta and the objdump interactions
are at best messy),
 - if libcapstone could solve our addr2line issues too this would be great :-).

Thanks,
Ian

> Cc: Changbin Du <changbin.du@...wei.com>
>
>
> Namhyung Kim (4):
>   perf annotate: Use ins__is_xxx() if possible
>   perf annotate: Add and use ins__is_nop()
>   perf annotate: Split out util/disasm.c
>   perf annotate: Use libcapstone to disassemble
>
>  tools/perf/util/Build      |    1 +
>  tools/perf/util/annotate.c | 1711 ++---------------------------------
>  tools/perf/util/annotate.h |   59 +-
>  tools/perf/util/disasm.c   | 1739 ++++++++++++++++++++++++++++++++++++
>  tools/perf/util/disasm.h   |  112 +++
>  5 files changed, 1914 insertions(+), 1708 deletions(-)
>  create mode 100644 tools/perf/util/disasm.c
>  create mode 100644 tools/perf/util/disasm.h
>
> --
> 2.44.0.478.gd926399ef9-goog
>